U.S. patent application number 10/579684 was filed with the patent office on 2007-06-28 for method of actuating and an actuator.
Invention is credited to Xiaoyang Huang, Yuejun Kang, Marcos, Kim Tiow Ooi, Teck Neng Wong, Chun Yang.
Application Number | 20070144906 10/579684 |
Document ID | / |
Family ID | 34619499 |
Filed Date | 2007-06-28 |
United States Patent
Application |
20070144906 |
Kind Code |
A1 |
Ooi; Kim Tiow ; et
al. |
June 28, 2007 |
Method of actuating and an actuator
Abstract
A method of actuating, comprising: filling at least a portion of
a tube (21) with a liquid (19) containing electrolytes, the tube
(21) having an inner surface that is electrically chargeable when
in contact with the liquid (19); positioning an object (28) in
fluid communication with the liquid in the tube; and applying an
electrical field (46) along a lengthwise axis across the tube at
said portion for producing a pressure in the liquid. The pressure
in the liquid exerts a force on the object so as to actuate the
object (28, 30). An actuator (20) is also disclosed.
Inventors: |
Ooi; Kim Tiow; (Singapore,
SG) ; Yang; Chun; (Singapore, SG) ; Wong; Teck
Neng; (Singapore, SG) ; Huang; Xiaoyang;
(Singapore, SG) ; Marcos;; (Singapore, SG)
; Kang; Yuejun; (Singapore, SG) |
Correspondence
Address: |
BLAKELY SOKOLOFF TAYLOR & ZAFMAN
12400 WILSHIRE BOULEVARD
SEVENTH FLOOR
LOS ANGELES
CA
90025-1030
US
|
Family ID: |
34619499 |
Appl. No.: |
10/579684 |
Filed: |
November 17, 2004 |
PCT Filed: |
November 17, 2004 |
PCT NO: |
PCT/SG04/00371 |
371 Date: |
May 17, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60520643 |
Nov 18, 2003 |
|
|
|
Current U.S.
Class: |
204/454 ;
204/601 |
Current CPC
Class: |
H02N 11/006 20130101;
F15B 2015/208 20130101; F03C 1/013 20130101; F03G 7/005 20130101;
F15B 15/18 20130101 |
Class at
Publication: |
204/454 ;
204/601 |
International
Class: |
C07K 1/26 20060101
C07K001/26; G01N 27/00 20060101 G01N027/00 |
Claims
1. A method of actuating, comprising: filling at least a portion of
a tube with a liquid containing electrolytes, the tube having an
open end and an inner surface that is electrically chargeable when
in contact with the liquid; positioning an object in fluid
communication with the liquid in the tube through the open end; and
applying an electrical field along a lengthwise axis across the
tube at said portion for producing a pressure in the liquid;
wherein the pressure in the liquid exerts a force on the object so
as to actuate the object.
2. The method of claim 1, wherein the inner surface is electrically
chargeable due to electrochemical phenomena.
3. The method of claim 1 or claim 2, wherein the tube is selected
from the group comprising: capillary tube and micro-capillary
tube.
4. The method of any one of claims 1 to 3, further including an
additional plurality of tubes each at least partially filled with a
liquid containing electrolytes in fluid communication with the
object.
5. The method of claim 4, wherein the plurality of tubes are formed
in a porous material.
6. The method of claim 5, wherein the porous material is made from
at least one material selected from the group consisting of:
silica, and ceramics.
7. The method of claim 6, wherein the porous material has at least
one material property selected from the group consisting of:
electrically non-conductive, porous structure, micro capillaries,
small particles, and hydrophilic.
8. The method of any one of claims 1 to 7, wherein the electric
field is generated from a power supply selected from the group
consisting of AC and DC.
9. The method of claim 8, wherein the DC power supply is linked to
an on-off frequency controller.
10. The method of any one of claims 1 to 9, wherein the pressure in
the liquid is caused by electroosmotic flow.
11. The method of claim 5, wherein a higher force on the object is
generated by adopting techniques selected from the group
comprising: using porous material with small pore sizes and using
porous material with large cross-sectional areas.
12. The method of claim 1, wherein a higher force on the object is
attained by using a lower concentration of the liquid containing
electrolytes.
13. The method of claim 1, wherein a higher force on the object is
attained by generating a stronger electric field.
14. The method as claimed in any one of claims 1 to 12 when as used
in an actuator.
15. An actuator comprising: a tube with an open end and an inner
surface and at least partially filled with a liquid containing an
electrolyte, the inner surface being electrically chargeable when
in contact with the liquid; an electric field generator for
generating a field along a lengthwise axis of the tube to induce a
pressure in the liquid; an object in fluid communication with the
liquid in the tube through the open end such that the pressure in
the liquid exerts a force on the object; and wherein the force on
the object is able to actuate the object.
16. The actuator of claim 15, wherein the inner surface is
electrically chargeable due to electrochemical phenomena.
17. The actuator of claim 15 or claim 16, wherein the tube is
selected from the group consisting of: capillary tube and
micro-capillary tube
18. The actuator of any one of claims 15 to 17, further including
an additional plurality of tubes each at least partially filled
with a liquid containing electrolytes in fluid communication with
the object.
19. The actuator of claim 18, wherein the plurality of tubes are
formed in a porous material.
20. The actuator of claim 19, wherein the porous material is of at
least one material selected from the group consisting of: silica,
and ceramics.
21. The actuator of claim 19, wherein the porous material has at
least one material property selected from the group consisting of:
electrically non-conductive, porous structure, micro capillaries,
small particles, and hydrophilic
22. The actuator of any one of claims 15 to 21, wherein the
electric field generator generates power supplies selected from the
group consisting of: AC and DC.
23. The actuator of claim 22, wherein the DC power supply is linked
to an on-off frequency controller.
24. The actuator of any one of claims 15 to 23, wherein the
pressure in the liquid is caused by electroosmotic flow.
25. The actuator of claim 19, wherein a higher force on the object
is generated by adopting techniques selected from the group
consisting of: using porous material with small pore sizes, and
using porous material with large cross-sectional areas.
26. The actuator of claim 15, wherein a higher force on the object
is attained by using a lower concentration of the liquid containing
electrolytes.
27. The actuator of claim 15, wherein a higher force on the object
is attained by generating a stronger electric field.
28. The actuator of any one of claims 15 to 27, further comprising
a housing defining a chamber containing the tube, and a cylinder in
fluid communication with the chamber, wherein the tube is in the
cylinder and the object is a piston slideably mounted in the
cylinder.
29. The actuator of claim 28, wherein the piston is biased to
resist a force exerted thereon from the tube.
30. The actuator of claim 29, further comprising a displacement
amplifier operatively connected to the piston.
31. The actuator of claim 28, wherein the piston has silicone
seals.
32. The actuator of claim any one of claims 19 to 21, or any one of
claims 22 to 25 when appended to claim 19, further comprising a
compensating piston to prevent a drop of pressure in the porous
material.
33. The actuator of claim 28, further comprising a vent in the
housing for allowing the exchange of air within the chamber.
Description
FIELD OF INVENTION
[0001] This invention relates to a method of actuating and an
actuator, and refers particularly, though not exclusively, to an
electrokinetic actuator and method for fluids. The use of such a
method and actuator is particularly relevant, though not
exclusively so, for compressing gases or vapour, for transporting
gases and vapors, for delivering non-conducting, non-polar liquids
in micro-scaled channels, and for enhancing mixing in
microfluidics.
BACKGROUND
[0002] Electroosmosis is an electrokinetic phenomenon that occurs
when an electrolyte fluid interacts with solid surfaces causing a
charged layer to form at the interface between the solid and the
liquid. Immobilized electric charges develop at the surface of the
solid surface in contact with the electrolyte fluid due to
electro-chemical phenomena. The surface charge leads to the
formation of an electric double layer ("EDL") by influencing the
distribution of counter-ions and co-ions in the electrolyte fluid.
In a diffuse layer of the EDL, the counter-ions predominate over
the co-ions to neutralize the surface charge. As such, the local
net charge density is not zero. A Columbic force is exerted on the
ions within the EDL when an electric field is applied tangentially
along the charged surface. Consequently, an electroosmotic flow
(EOF) results whereby the migration of mobile ions will carry the
adjacent and bulk liquid phase by viscosity.
[0003] The build-up of pressure as a result of electroosmosis
facilitates the transport and manipulation of liquids in
microfluidic devices for biomedical applications. These principles
have been applied in the operation of many electroosmotic pumps.
Such electroosmotic pumps work without movable mechanical parts,
consequently improving durability and minimizing difficulties in
production. Such electroosmotic pumps are essential for biochemical
analyses as they enable the pumping of liquids over a wide range of
fluid conductivities.
[0004] Given that electroosmosis is essentially a surface dominated
phenomenon, the use of a porous structure with a high surface
area-to-volume ratio can enhance the pressure-building capacity.
Paul et al. [1998 Electrokinetic generation of high pressures using
porous microstructures in: Proceedings of the Micro Total Analysis
Systems '98 Workshop, Banff, Canada] proposed a method to generate
high pressure using DC electroosmosis through a microchannel packed
with microparticles. The pressure of 10 atm at 1.5 kV applied
voltage has been achieved using fused-silica capillaries packed
with charged 1.5 .mu.m silica beads. S. Zeng et al, [Fabrication
and Characterization of Electroosmotic Micropupms, Sensors and
Actuators B 2001, 79, 107-114] fabricated an electroosmotic pump
that can generate maximum pressures in excess of 20 atm or maximum
flow rates of 3.6 .mu.l/min by applying a 2 kV electric voltage
over 5.4 cm long, 500-700 .mu.m in diameter fused-silica
capillaries packed with 3.5 .mu.m silica particles. S. Yao et al,
[A Large Flowrate Electroosmotic Pump with Micro Pores, Proceedings
of IMECE, ASME, 2001, New York, N.Y.] developed an electroosmotic
pump for a large flowrate with micro pores which can generate a
maximum flowrate of 7 ml/min and a maximum pressure of 2.5 atm for
200V applied potential. In a recent development, L. Chen et al,
[Generating High-Pressure Sub-Microliter Flow Rate in Packed
Microchannel by Electroosmotic Force: Potential Application in
Microfluidic Systems, Sensors and Actuators B 2003 88 260-265]
developed a pump made of microchannels packed with porous fine
dielectric material, which can generate a maximum pressure of 15
MPa.
[0005] The aforementioned sampling of documents show that the use
of electroosmotic principles are commonly employed in micro-fluid
pumping. Thus far, there has been no disclosure of the application
of electroosmotic principles for actuation.
SUMMARY
[0006] According to a first preferred aspect there is provided a
method of actuating, comprising: filling at least a portion of a
tube with a liquid containing electrolytes, the tube having an
inner surface that is electrically chargeable when in contact with
the liquid; positioning an object in fluid communication with the
liquid in the tube; and applying an electrical field along a
lengthwise axis across the tube at said portion for producing a
pressure in the liquid. The inner surface is advantageously
electrically chargeable due to electrochemical phenomena. The
pressure in the liquid exerts a force on the object so as to
actuate the object. The tube may preferably be selected from a
capillary tube or a micro-capillary tube. It is preferable that the
tube has an open end and the object is in fluid communication with
the liquid in the tube through the open end.
[0007] Preferably, there is an additional plurality of tubes each
at least partially filled with a liquid containing electrolytes in
fluid communication with the object, The plurality of tubes may be
formed in a porous material. It is preferable that the porous
material may be made from electrically non-conducting material such
as silica or ceramic. The porous material may advantageously have
one or more material properties such as a porous structure, micro
capillaries, small particles, electrically non-conductive, and
hydrophilic.
[0008] The electric field may be generated from AC or DC power
supplies. It is advantageous that the DC power supply is linked to
an on-off frequency controller. Advantageously, the pressure in the
liquid is caused by electroosmotic flow.
[0009] A higher force on the object may be generated by preferably
adopting techniques like using porous material with small pore
sizes, using porous material with large cross-sectional areas,
using a lower concentration of the liquid containing electrolytes,
or by generating a stronger electric field.
[0010] There is also provided an actuator comprising: a tube with
an inner surface and at least partially filled with a liquid
containing an electrolyte, the inner surface being electrically
chargeable when in contact with the liquid; an electric field
generator for generating a field along a lengthwise axis of the
tube for inducing a pressure in the tube; and an object in fluid
communication with the liquid such that the pressure in the liquid
exerts a force on the object for actuating the object. The inner
surface may be electrically chargeable due to electrochemical
phenomena and the pressure in the liquid exerts a force on the
object so as to move the object. The tube may preferably be
selected from either a capillary tube or a micro-capillary tube.
Advantageously, the tube has an open end and the object is in fluid
communication with the liquid in the tube through the open end.
There may be an additional plurality of tubes each at least
partially filled with a liquid, the liquid containing electrolytes
in fluid communication with the object. The plurality of tubes may
be formed in a porous material. The porous material may preferably
be made from electrically non-conducting material selected from
silica or ceramic. Advantageously, the porous material may have
material properties such as hydrophilic, electrically
non-conductive, porous structure, micro capillaries, and small
particles.
[0011] The electric field generator may generate either AC or DC
power. Preferably, the DC power supply is linked to an on-off
frequency controller. In addition, The pressure in the liquid is
preferably caused by electroosmotic flow.
[0012] A higher force on the object may be generated by adopting
techniques such as using porous material with small pore sizes,
using porous material with large cross-sectional areas, using a
lower concentration of the liquid containing electrolytes, or by
generating a stronger electric field.
[0013] Preferably, a housing defines a chamber containing the tube,
and a cylinder in fluid communication with the chamber. The tube
may be in the cylinder and the object may be a piston slideably
mounted in the cylinder. It is preferable that the piston is biased
to resist a force exerted thereon from the tube. The actuator may
further comprising a displacement amplifier operatively connected
to the piston.
[0014] Preferably, the piston has silicone seals. The actuator may
further include a compensating piston to prevent a drop of pressure
in the porous material. The actuator may advantageously further
include a vent in the housing for allowing the exchange of air
within the chamber.
DESCRIPTION OF DRAWINGS
[0015] In order that the invention may be better understood and
readily put into practical effect, there shall now be described by
way of non-limitative example only preferred embodiments of the
present invention, the description being in reference to the
accompanying illustrative drawings in which:
[0016] FIG. 1 is a schematic diagram of a preferred embodiment;
[0017] FIG. 2 is a graph of pressure gradient against time in a
micro-capillary of a preferred embodiment when a DC electric field
is applied;
[0018] FIG. 3 is a graph of pressure gradient against ratio of the
hydraulic diameter of a micro-capillary to a reference diameter
with a geometric size of 40.times.100 .mu.m when a DC electric
field is applied;
[0019] FIG. 4 is a graph of pressure gradient against
characteristic moments in a micro-capillary of a preferred
embodiment when an AC electric field is applied; and
[0020] FIG. 5 is a graph of pressure gradient against ratio of
applied frequency to characteristic frequency f* in a
micro-capillary of a preferred embodiment when an AC electric field
is applied.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0021] Referring to FIG. 1, there is provided a schematic diagram
of an electrokinetic actuator 20. The actuator 20 may have a
housing 22. The housing 22 may be of different cross-sectional
shapes, such as, for example, circular, rectangular, approximating
a square, polygonal, and the like. The housing 22 has a circular
cross section forming a cylinder.
[0022] The housing 22 defines a chamber 21 that encases hydraulic
fluid 19, a primary cylinder 24 and a secondary cylinder 26. The
primary cylinder 24 and the secondary cylinder 26 have different
bore diameters. The hydraulic fluid 19 acts as a damping medium.
The primary cylinder 24 has a larger bore than the secondary
cylinder 26. Correspondingly, a primary piston 28 in the primary
cylinder 24 has a larger diameter than a secondary piston 30. There
is also a primary retaining spring 32 and a secondary retaining
spring 34 in the primary 24 and secondary 26 cylinders
respectively. The primary retaining spring 32 prevents the primary
piston 28 from contacting a top end 40 of the primary cylinder 24
and to return the primary piston 28 to a resting position.
Similarly, the secondary retaining spring 34 prevents the secondary
piston 30 from contacting a top end 48 of the secondary cylinder 26
and to return the secondary piston 30 to a resting position.
[0023] The primary 24 and secondary 26 cylinders may be connected
as shown in FIG. 1. The top end 40 of the primary cylinder 24 may
have an opening (not necessarily central) joining to a bottom end
42 of the secondary cylinder 26. The primary 24 and secondary 26
cylinders may be filled with hydraulic fluid that flows within the
chambers of both the primary 24 and secondary 26 cylinders. The
hydraulic fluid may also line the walls of the chambers of both the
primary 24 and secondary 26 cylinders as a lubricating film. The
hydraulic fluid may be contained primarily towards the top end 40
of the primary cylinder 24 and the bottom end 42 of the secondary
cylinder 26. The primary piston 28 and the secondary piston 30 may
include at least one circumferential-seal 44 to prevent hydraulic
fluid from leaking to other portions of the chambers of the primary
24 and secondary 26 cylinders. The circumferential seal may be made
of silicone or other suitable materials.
[0024] Electroosmosis is ordinarily associated with DC (direct
current) electric field, which is used to generate a steady-state
mono-directional electroosmotic flow. An AC (alternating current)
electric field may also be applied to induce electroosmosis.
However, the electroosmotic flow then becomes time and frequency
dependent, with an oscillating flow direction. A
frequency-dependent excitation electric field may be applied across
a non-conductive capillary with single sealed ends to induce
electroosmosis. Each capillary may be filled with an aqueous
liquid. Since each capillary is sealed at one end, there is no net
flow of ions and this builds up the pressure in each capillary.
This pressure can be converted into an actuating force.
[0025] In a preferred embodiment of the present invention, the
primary cylinder 24 may contain hundreds or thousands of
microcapillaries bundled together in a lower end 36 of the primary
cylinder 24. For ease of fabrication, a porous material 38 (as
shown) filled/soaked with an electrically conducting or an aqueous
solution may be used in place of the microcapillary bundles. The
porous material 38 may be made of electrically non-conducting
materials.
[0026] Mathematical models have been developed to analyze the
frequency-dependent electroosmotic flow in empty or packed
microcapillaries. The corresponding Navier-Stokes equation is
solved using the Green's function method and the complete
Poisson-Boltzmann equation governing the EDL potential field is
solved under an analytical scheme for arbitrary zeta potentials.
When both capillary ends are closed, the oscillating flow
independently generated by the AC electroosmosis is balanced by the
oscillating counter-flow.
[0027] While operating the electrokinetic actuator 20, an AC power
supply 46 (or any sinusoidal power supply) with a switch 47 may be
applied across the porous material 38 which is filled/soaked with
an electrically conducting, any aqueous liquid, or any ionic
solution such as, for example, demonized water. With the AC power
supply 46 turned on, an oscillating electrical field generated
causes the ions in porous channels of the porous material 38 to
flow in an oscillating manner. As the porous channels of the porous
material 38 simulates closed channels, the oscillating electrical
field causes the liquid flow at the central part of these porous
channels in the porous medium 38 to change direction often,
creating a high pressure gradient in the porous channels in the
porous medium 38. This high pressure gradient generates a high back
pressure in the porous channels in the porous medium 38. The back
pressure in the porous channels in the porous medium 38 may be used
to push/move the primary piston 28 in the primary cylinder 24. The
primary piston 28 compresses the hydraulic fluid in the top end 40
of the primary cylinder 24 and the bottom end 42 of the secondary
cylinder 26. The compressed hydraulic fluid then pushes/moves the
secondary piston 30 of the secondary cylinder 26.
[0028] The secondary piston 30 may be connected to an actuation
cylinder 50 that provides linear actuation to external
applications/devices. The difference in the bore sizes of the
primary cylinder 24 and the secondary cylinder 26 creates a
displacement amplifier effect because of the non-compressitivity of
the hydraulic fluid. The volume of hydraulic fluid forced out of
the primary cylinder 24 by the movement of the primary piston 28
will be the same volume of hydraulic fluid forced in the secondary
cylinder 26. The smaller bore size of the secondary cylinder 26
compared to the bore size of the primary cylinder 24 allows the
actuator 20 to be used in situations where large amplitudes of
actuation are required. Based on the principle of conservation of
fluid, the amplitude of actuation of the actuating cylinder 50 is
the amplitude of motion of the primary piston 28 multiplied by the
square of the diameter ratio of the primary piston 28 and the
secondary piston 30. Hence, it can be seen that a slight movement
by the primary piston 28 would induce a significant movement of the
actuation piston 50, especially if the diameter ratio of the
primary piston 28 and the secondary piston 30 is large. The
converse is true when the secondary piston 30 falls from its
highest position.
[0029] In an alternative embodiment, a DC power supply instead of
an AC power supply may be used to work the actuator 20. The DC
power supply may be linked to an on-off frequency controller that
provides necessary on-off modulation for the system to simulate the
sinusoidal oscillating patterns of an AC power supply. The DC power
supply should preferably be of high voltage because of the high
electric field required. The actuation frequency may be specified
using the on-off frequency controller.
[0030] The lower end 36 of the primary cylinder 24 may include a
compensating piston 52. The compensating piston 52 may be used to
prevent the drop of pressure in the porous channels of the porous
material 38 during the operation of the actuator 20 due to the
displacement of the primary piston 28.
[0031] A vent 54 may be incorporated at the lower end 36 of the
primary cylinder 24. The vent 54 may be used to facilitate the
movement of the compensating piston 52. The vent 54 allows the
compensating piston 52 to return to its rest position when the
primary piston 28 returns to its own rest position by exposing the
void in the housing 22 created by the movement of the compensating
piston 52 to atmospheric pressure.
[0032] Simulations have been carried out to determine the
characteristics of different parameters in a sealed micro-capillary
during frequency-dependent electroosmotic flow. The simulations and
calculations were carried out based on a set of fixed parameters.
The working fluid was NaCl (sodium chloride) with valence of 1 at
293 K and with density, viscosity and dielectric constant of 10000
kg/m.sup.3, 9.times.10.sup.-4 Ns/m.sup.2 and 80, respectively. The
reference velocity was set at 1 mm/s and the electric field for
both DC and AC were applied with a field strength of 1000V/m. The
characteristic hydraulic diameter of the micro-capillary was set at
57 .mu.m. Other important parameters were a characteristic time
t*=155.3 .mu.s with a corresponding eigen-frequency of f*=6.44
kHz.
[0033] FIG. 2 shows that in the instance of a DC electric field
applied to a micro-capillary, the highest magnitude of the pressure
gradient (80) is generated during time first instant immediately
after the application of an electric field. It can be seen from
FIG. 2 that the pressure gradient gradually decreases thereafter
and eventually attains a steady state of a low pressure
gradient.
[0034] FIG. 3 shows a graph of pressure gradient against a ratio of
a hydraulic diameter of a micro-capillary to a reference diameter
with a geometric size of 40.times.100 .mu.m when a DC electric
field is applied. The negative gradient of FIG. 3 suggests that as
the size of the micro-capillary increases, the magnitude of the
pressure generated in the chamber decreases.
[0035] FIGS. 4 and 5 show the behaviour in the micro-capillary that
occurs when an AC supply electric field is applied to a
micro-capillary. FIG. 4 shows a graph of pressure gradient against
characteristic moments in a micro-capillary of a preferred
embodiment of the present invention when an AC electric field is
applied. FIG. 4 shows that at higher excitation frequencies, for
example, when f=10f*, the larger the oscillation in values of the
pressure gradient.
[0036] FIG. 5 shows a graph of pressure gradient against a ratio of
applied frequency to characteristic frequency f* in a
micro-capillary of a preferred embodiment of the present invention
when an AC electric field is applied. As denoted in FIG. 5, the
supply frequency should exceed the characteristic frequency f* in
order to attain a high pressure gradient within a micro-capillary.
It can also be seen that when the ratio of applied frequency to
characteristic frequency f* (dimensionless excitation frequency)
exceeds the value of 100, the magnitude of the pressure gradient
increases linearly with the magnitude of the dimensionless
excitation frequency, and correspondingly, the supply
frequency.
[0037] The force required for the actuation of the primary piston
28 may depend on various factors. Higher forces may be attained by
utilizing a porous medium 38 with small pores sizes. It should be
noted that the overlapping of EDLs should be avoided to maximize
the amount of force generated. Other approaches to attaining
greater forces include using a lower concentration of the
electrolyte solution, using a larger cross-sectional area of a
porous column, and using a stronger electric field. Forces in
excess of 2 KN may be obtainable from the use of a 0.1 m diameter
porous column.
[0038] The actuator 20 is a simple design with few moving parts
that is not complicated in construction. Each actuator 20 requires
minimal maintenance, if any. The materials used to manufacture the
actuator 20 may include metals, silica, ceramic and plastics. The
materials used and the corresponding material costs would be
determined by the environment that the actuator 20 is employed at
The cost of manufacture would be low-as the actuator 20 may be
manufactured using existing manufacturing techniques and
technology.
[0039] The actuator 20 is an energy-efficient device. Although the
applied voltage to generate an electric field is relatively high,
the current drawn is low and correspondingly, power consumption is
low as well.
[0040] The actuator 20 may be used in a myriad of different
applications ranging from situations that require precision micro
actuation, to situations that require large displacement linear
actuation such as in a linear motor. It may be unnecessary to use a
displacement amplifier in the actuator 20 for precision micro
actuation. The actuation may be obtained directly from the primary
piston 28.
[0041] The actuator 20 may be used in applications involving linear
actuations. The actuation may be in nano, micro or macro scales.
The actuator 20 may also be used for positioning in relevant fields
of applications.
[0042] The actuator 20 may be used as a precision actuator as its
actuation can correspondingly be controlled precisely since the
displacement of the actuator 20 is proportional to the applied
electric field strength. As such, the actuator 20 may be employed
to replace piezo-actuators. The actuator 20 may also be employed in
a hard disk drive to position the head arms to different tracks on
the surface of the platter during the writing/retrieval of data.
Similarly, the actuator 20 may be used as a precision
micro-actuator in cameras, microscopes or any applications that
require precision linear or possibly even rotational actuation. For
larger amplitudes, of actuation, a linear displacement amplifier
(as described earlier) may be used to amplify the amplitude of
displacement.
[0043] In an alternative application, the actuator 20 may be
employed as a linear motor. It may be possible to generate larger
linear displacements from the actuator with the aid of a mechanical
displacement amplifier. The actuator 20 may be used in various
scales as a linear motor in delivering linear actuations such as,
for example, driving linear air compressors or refrigeration
compressors for air-conditioners or refrigerators or in a miniature
refrigeration system for CPU cooling. The fabrication of the
miniature refrigeration compressor may be possible because of the
miniaturisation of the actuator 20. The actuator 20 may also be
used for hydraulic or pneumatic actuations.
[0044] The actuator 20 may also be used for precision positioning
applications. As the pressure generated by such actuators 20 may
attain very high levels (in excess of 100 atmospheric pressures),
it may thus be suitable for applications in static and dynamic
nano, micro and macro positioning, depending on the design
parameters of the actuator 20.
[0045] Whilst there has been described in the foregoing description
preferred embodiments of the present invention, it will be
understood by those skilled in the technology concerned that many
variations or modifications may be made to details of design or
construction without departing from the present invention.
[0046] The present invention extends to all features disclosed
either individually, or in all possible permutations and
combinations.
* * * * *